In the production of oil from a well, a subsurface pump is commonly used. The pump is placed at a location below the level of oil in the well and has a plunger which is connected to a string of sucker rods extending upwardly through the well tubing. The sucker rod string and consequently the pump plunger is reciprocated by a well pumping unit and associated apparatus at the surface. The well pumping unit includes an oscillating walking beam having an arc attached at one end of the beam. A cable or rod supported on an outer curved surface of the arc is connected to the sucker rod string so that oscillation of the beam causes the pump plunger to reciprocate in an upward and downward direction forcing oil to the surface. To perform repairs on the well, it is necessary to move the arc in order to make the upper end of the well conveniently accessible. In the past, this has been done by removing the arc from the beam or by moving either the arc or beam away from the well. These operations have been very hazardous because of the need for personnel to work under or around the arc while it is in an unstable position. Two primary approaches have been taken in the design of pumping units for alleviating the hazardous nature of this operation. In one approach, the beam is moved laterally away from the well without detachment of the arc. Examples of this design are shown in U.S. Pat. Nos. 2,070,815, 2,169,815, 2,071,437 and 2,057,917. A disadvantage of these designs is that additional apparatus is required for moving the beam. Also, support for the beam is necessarily less rigid than when means is not provided for such movement. A second approach, shown in U.S. Pat. Nos. 3,006,201, 2,079,276 and 4,092,872, involves rotation of the arc upwardly about a pivot to a position in which it rests on top of the beam. This operation usually requires attaching cables to the arc so that it can be moved by a crane, necessarily requiring a workman to be in a hazardous position under the arc. In the event that the beam should unexpectedly move downward, the arc can swing like an ax posing a serious potential danger to workmen in the area. U.S. Pat. No. 4,092,872 shows a conventional arc latch which is not remotely actuable. This reference discloses removal of the arc in order to gain access to the well head. To remove the arc, a workman must remove a pin which holds the spring-biased arc latch in a position against the walking beam. To do this, he must climb onto the arc or stand on a ladder resting against the arc, placing him in a hazardous position.
It is a primary object of this invention to provide a well pumping unit in which the arc is safely movable out of operative position without requiring a workman to climb onto the arc or stand immediately adjacent to it.